Bulk Mixing Considerations
Improper resin ratios may lead to issues with both print quality and material properties. Specifics depend on the resin and how imbalanced the ratio is, but can result in decreased accuracy (increase in cure-thru and overcure ) and decreased toughness or stiffness.
- In general, stay within ± 1.5% of target component amounts for best results.
- EPU-family durability is more sensitive to imbalanced mixes.
- EPX-family accuracy is more sensitive to imbalanced mixes. However, unless the offset accuracies would be quite small (10s of microns) unless the imbalance was greater than 5%.
Thorough, uniform mixing is important for best results. One way to evaluate mix quality is by addition of a fluorescent dye, but this is only for establishing a thorough mixing protocol through visual inspection. Resin mixed with dye cannot be used for printing.
- Testing should match actual mixing conditions (container, resin volume, mix time) as closely as possible.
- Once tested, this protocol can be used moving forward, and eliminates resin waste due to burn off from cartridges.
- Incorporate 0.1 wt% of Fluorescent Brightener 184 into Part B
- CAS: 7128-64-5, available through Sigma-Aldrich
- Mix using desired method.
- Visualize with 365 nm light source (search “365nm UV flashlight”)
- Below are examples of incomplete and complete mixing:
Incomplete mix - Swirl pattern indicates components are not fully blended together.
Complete mix - Absence of patterns shows components are properly blended into a uniform whole.
Crystals may form in the Part A component if it is exposed to low temperatures during shipping. The following resins are subject to crystallization:
- EPU 40
- EPU 41
- EPU 43
- EPU 44
- EPU 45
- EPU 46 Black and Color Base
- RPU 130
Crystals can be melted by the application of heat. Smaller containers (1 L, 5 L, and 19 L) can be warmed in the same oven used for thermal curing printed parts. Drums and IBCs require warming blankets.
- Place the container of the crystallized component in the oven or incubator.
- Set the time and temperature. 3 hrs at 40°C is a good starting point.
- Run the oven.
- Carefully remove the container from the oven and check that the crystals are melted. If necessary, continue warming until crystals are melted.
- Carefully remove the container from the oven or incubator. Use caution as the container may be hot.
- Agitation of resin may be necessary.
- Before dispensing the resin, cool the container to room temperature.
- Store cartridges at the recommended temperature to prevent recrystallization.
Consult the specific course, protocol sheet, or resin processing handout for instructions.
Vigorous mixing may lead to the formation of bubbles in the mixed resin.
Bubbles are typically displaced from the layer of resin that is being cured during the print process. However, in extreme cases, these bubbles may be in/on the printed part and lead to mechanical or aesthetic defects.
- Surface defects are likely geometry specific and are most noticeable on cassette-facing flat surfaces.
- Extreme mixing conditions and bubble formation may lead to pigment separation which will affect printability and part aesthetics.
When using an overhead mixer, high mixing speeds or mixing smaller amounts of resin may result in splashing.
- To mitigate spraying or splashing, start mixing at low-speed and be wary of splashing of Part B.
With repeated opening and closing of the stock container, the Part B component can form a salt. Small amounts of salt may be present in mixed resin and are acceptable for printing because the salts decompose during baking.
Large amounts of salts can result in incorrect ratios so proceed with caution.
If you have questions about salts in Part B, reach out to Carbon Support.
Acceptable Levels of Salt
Unacceptable Levels of Salt
We suggest downpacking into smaller containers to minimize the chances of salting. Remember, Part B components must be stored in UV light-resistant containers, such as opaque amber nalgenes.
- The L1 cassette weighs at least 45 lbs. Always use the L1 Cassette Cart to maneuver the cassette when not in the printer.
- Two additional lab consumable accessories are recommended when printing with an L1 printer.
- Wide spatula
- For checking the window between prints.
- For removing leftover resin.
- Resin transfer container
- Optionally for dispensing.
- When using a scale to measure dispensed resin.
- For removing unused resin.
- Can be disposed of after use (in solid hazardous waste).
- Note that one full cartridge is the minimum amount of resin needed in the cassette, to cover the window, throughout a print.
- Leftover resin can be transferred to an M Series printer, if available, when there is enough pot life left for the resin.
- Expect more time for dispensing than with an M Series printer.
- Multiple dispensers or an MMD are recommended to save time.